Apparatus for and method of baking



y 1961 P 0' H. DRESSLDER ETAL 2,983,022

APPARATUS FOR AND METHOD OF BAKING CARBONACEOUS PRODUCTS OR THE LIKE Filed Feb. 28, 1958 9 Sheets-Sheet 1 5 \Q q E 5 1 3 m fix i I\ w J Q g T T "1/- l E L INVENTORS N PHIL/P d 14.02555452 JoHusAuazv/g/E m /=W THE/E A r mews vs P. D' H. DRESSLER ETAL APPARATUS FOR AND METHOD OF BAKING May 9, 1961 CARBONACEOUS PRODUCTS OR THE LIKE 9 Sheets-Sheet 2 Filed Feb. 28, 1958 THE/,2 A 1-1-02 usvs M y 1 P. D' H. DRESSLER ETAL 2,983,022

APPARATUS FOR AND METHOD OF BAKING CARBONACEOUS PRODUCTS OR THE LIKE Filed Feb. 28, 1958 9 Sheets-Sheet :s

PH/L md 74. DEESSLEB Jo Hu 5. ANG'El/IA/E y 9, 1961 P. D' H. DRESSLER ETAL 2,983,022

APPARATUS FOR AND METHOD OF BAKING CARBONACEOUS PRODUCTS OR THE LIKE Filed Feb. 28, 1958 9 Sheets-Sheet 4 a 3 RE 8 v vQ 3 S, vs fin i M INVENTORJ PH/L/Pd'H. Dee-same JOHN 5. AA/G'EV/HE B WW$PW THE/.2 Arr-gays vs M y 1961 P. D H. DRESSLER, ETAL 2,983,022

APPARATUS FOR AND'METHOD OF BAKING CARBONACEOUS PRODUCTS OR THE LIKE Filed Feb. 28, 1958 9 Sheets-Sheet 5 INVENTORS FL 9. 4 PH/L/PdH. 0255.51.52

JoHu 5. ANGE VIA/E THE/2 A r TOE/JETS 9 Sheets-Sheet 6 P. D H. DRESSLER ETAL APPARATUS FOR AND METHOD OF BAKING CARBONACEOUS PRODUCTS OR THE LIKE IN VEN TORJ' T E/g A TTORNE vs P /Z/Pd H. 025551.52. Jar/N 5. ANGEV/NE 2/ w w May 9, 1961 Filed Feb. 28, 1958 liiifi wiiiiii il y 1961 P. D H. DRESSLER EIAL 2,983,022

APPARATUS FOR AND METHOD OF BAKING CARBONACEOUS PRODUCTS OR THE LIKE Filed Feb. 28, 1958 9 Sheets-Sheet 8' 9 j, =UZ ==g 1E "337/, f 29 A INVENTORS 7,, pHlLlPd'l-LDEELSSLEE. JOHNS-ANGEV/NE F 14 W THE/E Arraeusvs y 1961 P. D H. DRESSLER EI'AL 2,983,022

APPARATUS FOR AND METHOD OF BAKING CARBONACEOUS PRODUCTS OR THE LIKE 9 Sheets-Sheet 9 Filed Feb. 28, 1958 I INVENTORS PH/L lPd H. D255 54 E2.

.JoHu 5. A -65 VIA/E THE/e A r-roeus v.5

United States Patent APPARATUS FOR AND METHOD OF BAKING CARBONACEOUSAPRODUCTS OR THE LIKE Philip dH. Dressler, Pittsburgh, Pa.,' and John S. Angevine, Newburgh, Ind.; said Dressler assignor to Swindell-Dressler Corporation, Pittsburgh, Pa., a corporation of Pennsylvania, and said Angevine assignorto Aluminum Company of America, Pittsburgh, Pa., a company of Pennsylvania Filed Feb. 28, 1958, Ser. No. 718,170

18 Claims. (Cl. 25-142 This invention relates to a new system for baking carbonaceous products or the like. More especially, this invention pertains to a method and tunnel kiln or relatively continuously producing finished carbonaceous products, such aseIectrodes suitable for use in the production of aluminum, or other articles used for other purposes, without the use of saggers or containers.

-Heretofore, carbon electrodes, for example, have been prepared as a practicalmatter by the mixing of calcined particles of petroleum coke or other carbon with a binder of pitch and then pressed into the shape desired for'the electrode being-'madei Such molded green electrodes have then been placed" inpit furnaces close to one another, and packed in and covered with coke. The electrodes were heated indirectly by conduction of heat from the furnace. fines; The baked electrodes so produced varied somewhat in density from top to bottom and side to side. Those electrodes which were too soft or spongy had to be rejected. Acceptable electrodes, on the other hand, left the baking operation with a relatively rough dull surfacewhich required expensive cleaning or grinding to make them smooth and to clean out therecess where the electrodes normally are attached to the conductor bar- 'stub. Such batch-produced electrodes also varied from electrode to electrode in a particular batch and reproducibility by"successive'batches was substantially unpredictable. As for the electrode baking fur naces, they operated with high fuel and maintenance I costs and the production therefrom was low in' view of In the new systemof this invention,frelatively' con tinuous production of various carbonaceous products,

such as electrodes for the making of aluminum orthe like, is obtainable on a cycle measuredin' a matter ofa few days; The new system is noteworthy in=thatit makes i I Figure 1C; 1 v

Figure 6 is a view in elevation taken along line VIVI of Figure 1B;

2,983,022 Patented May 9, 1961 In product, process and appara ment in terms of increased quality, continuity, uniformity and speed of production.

tOther objects,rfeatures and advantages of this invention will be apparent from the following description and the accompanying drawings, which are illustrative of one embodiment only, in which I Figure 1, comprising parts 1A, 1B, 1C and 1D, shows one embodiment of this invention in plan with the righthand portion thereof fronrthe center in section taken along line II of Figure 2 and with the product conveyor removed;

a Figure 2, comprisingparts 2A, 2B, 2C and 2D, shows the embodiment illustrated in Figure 1 in elevation and in section taken along line Ill-II of \Figure 1, with a few product conveyor cars schematically shown in the furnace zone;

Figure 3 is a cross section through the initial preheat-- I IV-IVof Figure 1B; t

Figure 5 is a cross section taken :along line V-Q-V of Figure 7 is a view in VIFIofFigureti; A Figure 8 is a view in elevation-taken along line VlIII- VIII of Figure 1B;

Figure 9 is a view taken along line IXIX of Figure 8; y A

- Figure 10 is a view in elevation taken along line XX of Figure 1C; I I a Figure 11' is a view in sectiontaken along line XI-XI of Figure 10;

Figure 12 is a partial view in elevation taken along line XII-XII of Figure 2A;

Figure 13 is a detail view in XIII- XIII of Figure 2A;. t

Figure 14 is a detail view in elevation taken along line X1VX[V of Figure 2A;

Figure 15 is a detail view in plan taken along line elevation taken along 5 line of Figure 2C; 7

Figure 16 is .a schematic view of the right-hand half of Figure 4 illustrating the regulated outward flow from .the mufilecombustion chamberto the nearby product the baking of such products possible, without the'use of saggers, containers or other lateral supports and, further, provides a clean operation, bo'thftrom the point'of view of industry and the personnel employed therein. S'uch products and electrodes, moreovenf are finished in that they require o lcle"aning or smoothing, have a "metallic gray silvery appear nce and are mo're uniform from top to t m Z 1 r r slde ds e 5. du e t li e -i ng oi' breaking ea in usein the i d have, a? more predictable life and tune? I tional character.. In} the-new, furnace means disclosed] herein, gprovision is made to avoidruntiniely; shutdowns I e t -n r n d rqsit an rsa fla a a t gl e to inhibit such depositslpnd'transpottof oublesome' mar ts i i w e newfiuu c ov s nu t e. a n n -a t,. rp fi fil -combu t n: Y pp s elati l e lea a h ius si- -P d uct passingQ-through also made for,

e ewstem. os s wd e bak ng and v o;s lisa iol w thi-y hcateertoni ioa sfiv p kiln 10. having an entry vestibule 11 at the frontthereof 'and' an exit vestibule 12fat the back thereof.;. Steel ofthis, invention; and

space;

Figure 17 is I ceous electrodewhich may be made by the new system Figure 18is a s'chematic flow-diagram torthe illustrated embodiment. i i

Referring to the drawingsone'embodirnent for a practice of this, invention is shown in the form of a tunnel girding forfurnac'e. 10 is. provided ;in the formfofverti cal buckstay's 13'and tieing root girders E14 and lfio or gir ders' 5115. Attack; 16 extends. longitudinally through, fu'rA mee 10 for a conveyor intheiformof cars;17 whichroll on: the1tra ck16. "The car'sfilfl. have machined ,ends .18 I

virtual end to; end closure between carsja the; other throughfthe kiln upon the introsection-taken along line VII- a perspective view of 'onefform of carbona- 3 by step through furnace '10 in a relatively continuous moved. Thetarry liquids may be kept relatively free finishing and industrially. clean operation. flowing if needed by the use of a steam coil 50 placed Furnace 10 is gas-tight and vestibule 11 is provided in the bottom of the undercar space in that section. withan outer door 20 and an inner door 21, -while vesti- A side trough 51 extends along the inner face of each bule 12 is provided withau outer door 22 and an inner bench 29 to overlap the lower edge of a seal plate 52 door 23. These vestibule doors are operable manually, carried on each side of each car 17.---In thepreheating semiaautomatically or automatically and in sequence so zone 33, the side troughs 51 begin a shortdistance after that when the outer door of each vestibule is open, the the beginning of the section itself. Such troughs 51 are inner is closed and. vice versa. Cables 24 operate the empty. in'the preheatingsection 33 and are sealed by at least through pipes 25a and 26a respectively,

respective vestibule doors; the inner ones being within the the run-oft tar Which drains into trough" 48 from the closed superstructures 11a and 12arespectively.. A purge troughs 5-1 through holes 53 in the bottom thereof. Thus,

atmosphere, which is non-combustion supporting, is supa seal between the undercar space and'the space above plied .to each vestibule through the respective pipes 25' the top of the benches 29 is establishedbefore any car and 26 before communication is made between the rehas moved very far into preheat section 336% furnace 1t spective. vestibules' and the interior of'the furnace he'- Intermingling of the atmosphere above-the body of tween them; the purge atmosphere exhausting in part car 17 and the atmosphere in the undercar space 30 is fur- V v v 7 ther inhibited by the provision of nozzles 54, shown in The steel girding of furnace "10 binds the tunnel walls detail inFigure 12, which discharge relatively cool, clean, 27 and arch roof 28; of refractory. Each of those walls non-c mbustion supporting gas toward the entrance end. 27 is provided with a laterallyand.longitudinallyextend Such not only keeps the underca-r space throughout the ingbench 29 in each section of the furnace. The opposed furnace 10 relatively cool, but it also substantially inhibits benches 29 define a longitudinally extending undercar such intermingling and circulation of product space atmosspace 30 below the tops and between the inner sides therephere along the undercar space; and it further inhibits of. p A product space tunnel-31 extends lengthwise through air infiltration into space 30 and furnace 10. As a confurnace 10 inwardly of the vestibule'ssabove thetops sequenc,".the underbody of each car is kept relatively of the benches 29 and is separated normally from the free from "deposit of tarry materials as .well as relatively f undercar space-130 by the presence 'of thekca'rs 1-7 whose cool, 'And, in themufiiepreheating andiheating zones bodies continuously fill the length of furnace lfl-fromone 35A and 35B; longitudinally extending pipes 55 are pro inner door 21 to th eother iriiier door 23 andthe width vided tthrough' which coolingffluidllike airfis forced to g between the benches. As each foremost car is; separated assist, in maintaining the undercarspace coolerinthose and moved into vestibule "12 through door; 23 while door normally hotter sections of furnace 10." Q v I 22 is closed a fresh caris rnoved rearw-ardly in'td ins'u 7 A se 'esof roof jets SIG LfOrnOn-combustion supporting lated passagel32atthebeginningof furnace 10 prope'rw gas. extending down through the crown of roof 28 m As a car moves rearwardly through furnace 10 'itpa'sses I sections'l 33. and A are shown in illustrative detail .in'

first through a preheating zone 33 having longitudinally; Eiguref14 aridfire toward the exitend of furnace 10. extending pipes 34 therein. Preliminary preheatingfof In so doing, those roof jets 5 6 insectionsl3 3 and 35A the product 19 a takes 'placein zone 33 and-lower boiling minnniz any. tendency to set 'up a longitudinal circula hydrocarbons or other volatiles may be drive'nfoff. ,h in tion within the respective sections of a stratified nature addition, atmosphere entering the product spaceportion along" the underside of the roof crown. A like roof jet 31a in zone '33from other hotter zones in furnaceitltl will 40 56 adjacent thefront of the cooling section 43 discharges be carrying condensible materialtherei'ri generally-of a non-combustion supporting gas toward the front end of tarry character, Quantities of those condensibles upon furnace '10.

reaching relatively cooler zone 3 3 will condense and'run N Admission of a combustion supporting gas like air in down tov the bottom of the conveyor zone 30 where Tthey any materialquanti ty into either end of furnace 10 is preean be collectedand'rernoved. I vented not only by the double-dooredvestibules 11 and In a second preheat zone 35A having a; mufiie 35 err '12 but also by the provision of curtain nozzles 57 ;which each side, thep'roduct' on-the cars 17 is raised'in temper- I are shown in detail in Figure 13 and thepositive presature at a predetermined rate and removesfurtherfhigher"' usure in. 11 a p oduct space .undercar space. Such. boiling volatiles. Continued rearward nrovement ofia nozzles 57 have downwardly.directed slots 58; through.

I carwillbring it'alongside a furnace'secti n SS B having which non conrbustion supporting gas in'relatively clean a mufile- 37 on' each side with a hollow tile'mufilejwall' condition is supplied. v Such gassq supplied to the cur- 4'0 and cap 41p 1n the product space 310 intfurnace" sec-'- V tam-nozzles 57 *r nay come from an atmospheregenerator tiOllj'SSB, thetemperatur'e of the ele'ct'rodeson thef cars17 suchas thosewhichmake DX or other suitable atmos- V is further raised .tintil'it re'aches'a m iuniurnbeginning cooling pipesf43ax Inthe'cooling produc 31d; .the produ ct is v reducedfin temp'eratu 1 V v is passedf into vestibule 12 and front thence into th out h r r aeerit ma be n w m o rjsuppo t n a about. oppo it iha in rs 'T t tsmi r tqfl 5 ken i m h rint r f ur t-a d gle ed be o e. be maintained substantially until the" car i being-recirculated to;the'curtainnozzles 57; underproduct space 31d in the cooling sect car nozzles 54 and theroofjets 56, vas well as t he purge a p pc 25 6,- y b s m a liedom eit er ll fi 1.x. :.:i a 60f n connection with thepressurenozzles -54, they las shown figure may 7 comprise a sh "Triei whiclrtheliquid i pje V eet metal p churne 5 gas eriters tipen bafiies'75 which follow the crown line of roof 28' from .5 i s 65,-.i h; I i t the slotted ,areua te at.the bottom thereof, such orifice being oriented in the selected direction as aforesaid. I .In preheating section 35A, the muffle wall 37 is built of suitableqtile teiprovide a-muflle heating .zone 36 covered by a cap .tile 38. The .ends of longitudinally succeeding :cap tiles 38 are provided .with stepped portions 38a so that" there are staggered interstices of a tortuousflnature between such cap tiles. like the interstices 40a in hollow tiles 40. Like interstices may be provided, if, desired, between the, tiles of wall 37. Such cap tiles .rest onthe top of wall 37v on the one side and on a ledge 27a on the other-side. Thebottom of the walls 37 issupported in an appropriate recess 37a in each of the benches 29. In ItheJm-uffle preheating section 35A further volatile material is driven off of a tarry character which contaminates the atmosphere in product space 31b within that preheating; section. In order to eliminate much tarry material as quickly as possible, section 35A is provided with a series of waste burners 67 shown in detail in Figures6 and 7., Such burners 67 comprise a gooseneck rnember 68 extending through the walls 27 for that purpose. The members 68 discharge into a venturi block69 and in so doing create a suction in the passage70 and duct 71 which has an adjustable opening controlled by a duct damper 7 2. The upper end of duct 71 ;is in communication witha cross duct 7111 which is open to product space 3112 Damper 72 is movable by a rod72a so that it can be set to a preselected position. Thus, there is alateral withdraw'alto each side of the section 35A product space 31b of atmosphere'containing the tarry volatiles'to provide fuel for the operation'of burners 67. Such firing taking place in muffle space 36' toward the front end of each thereof where offtake ducts 73 are located, such offtakes on each side terminating in an ,ofitake drum 73a for further handling of such com-, busted material. A. pilot burner 74. insures ignition of the combustibles issuingfrom each burner 67. Thereby, tarry materials which otherwise would deposit on the surfaces of the rnuffle 36 are quickly removed instead and burned. l

The roof jet. 56 insection 35A dischargingas it does toward the exit end of thatjsection inhibits longitudinal circulation and a tendency of tarry laden atmosphere from section 35A to drift or flow toward furnace section 35B in whichthe muffle and furnace surfaces are hotter with resulting greater detriment should tarry materials land thereon because of the cracking and harder carbon depositiontthat would be likely to result. Such movement of contaminated gases from section 35A toward section 35B is also impeded bythe downwardly projecting roof one sideof the interior offurna cef to the other. f

Supplementary, or alternative, means, for; taking care of the tarr am atmosphere inipreheating section 35 are also shown in that such gases may if desired be'with-i drawnthroughajioof olftake'76 a detail of which is'illus trated in Figure 1 5. A further such roof ofitake'for product space atmosphere'withdrawal'is provided insection 353. Each such offtake has a central ,opening"77 at the very top of the crown of roofi28 which'is'closed bya fitting 78 which fittings internal flange 79 fits around opening" 77 so that a"clos'ure"80 rnay if desired .slide' in to seal. theged'ges of flange 79." 'Theinternal fitting'78 exhausted thnough-apipellil which normallywould be under suction 'Thejpressure in the product space 31 is normallifmainta ned slightly above atmospheric pressure from re. end offthefurnacelll to'the other to; prevent PP like the cap nozzle '56 beforeissuing from menses ef treprbg aisba r to provide staggered or overlapping joints. At the same time, the cap tiles rest onthe muffle chamber and furnace walls [sojthat expansion and contraetion are permitted to occur freelyfto the extentthat they'may take place. In constructing the walls of each 'mufiie chamber .39, pieces of a material like cardboard may be inserted between the joints of the respective tiles so that when the furnace is dried out prepartory to use, such burnout or filler pieces will be consumed and. provide staggered interstices through which gasmay flow for a purpose which will hereinafter be described. The hollow wall tiles may be provided with upper and lower openings 82 on theoutside thereof so that'the space between the front and back walls of each tile 40 will act somewhat in the manner of a flue. I

The muffle chambers 39 are heated by the burners I shown in more detail in Figures 10 and 11. Those burners comprise a gooseneckmember 83 through which a rich fuel gas mixture may be supplied with insliflicient' air therein to be combustible. Secondary air for such combustion is supplied to the burners 42 through a duct 84 which, like the member 83, extends through the side wall of the furnace 1 0, such wall being closed around the respective member and "duct. A sighting hole 85 may also be provided and normally closed on the outer end thereof adjacent each burner 42. The fuel dis charged from the member 83 passes through a venturi block 86 and aspirates secondaryair to combust thefuel and air in the mufile chambers-39. Each of theburne'rs 42 may be provided with suitable valves on the fuel and air supply members to enable them to be individually regulated if and as desired. The regulation of such burners, further, is but one means for regulating the pressure in the respective mufiie chambers 39. a

At the forward end of the respective muflfie chambers '39 there are ducts 87 leading to olftakes 88 which on bers 36 in the illustrated embodiment, each said passage 90 being controlled by a sliding pressure regulating damper 91 controlling the opening 92 in passage 90 Damper 91 is movable, in a recess 93, the outside of which is covered by an insulated cover 94 fastened to the steel shell of the furnace,such steel shell preferably covering all of the outside of the refractory and brickwork of furnace 10. The rear of thedamperis provided with socket eyes ,95 to be engaged by thehooked ends of rods passed through openings 96 when the caps 97 are removed therefrom so that the amount of opening 92 may be adjusted in accordance with the desired pressure relationship among the respective muflle chambers and the respective product space portions alongsideand adjoining them in furnace 10; -:In somecases, damper 91 maybe entirely closed,- thereby making the'muflle chambers in eachof 5 the respective" furnace sectionsSSA and 35B ineliect sep arate and independent muffie chambers.

. The maintenance of electrodes19- at maximum optimurn temperature opposite theburners, 42in product space 31d of; section-35B completes their.,.discharge of:

volatile material and densification in'the-Tcourseof'unden going heating uniformly from top to bottom {and side to side in the course of their progress through thel urnace, i

10 and gives themazsupe'rlativezand unique finish. Such heating is facilitated by mountingfl the electrodes on the 'cars'1'7. on mountsancl so "spaced'that the atmospherein the product space can circulatefreely between the 'r-J spective electrodes:or stacks of electrodes, such. heating- I taking place chiefly by convectioniarid radiation with 7 'port'ant increase in heating effectiveness Over prior 1pm; teeny-Furt er, hydrocarbon'and particulatelmaterial o a combustible nature; which gets iin'to the atmosphere in the prodiict space- 31c lalongside ,.the; muflle; chambers 39 I of theniuflle=tileskby providing for? acontrolled ept fromi detrimental;adherence-tome iouterf f,

thereof iii close proximity to such facei; f'riierby;

the turbine walls of'the'chamber 39 are keptrelatively clear of caribon'aceousldepositv for the transmission of heat therethrough-- and therefrom to the" passing electrodes. f I

'Inthe case" of the mettle chambers 39, they are maintaineda't a pressure slightly ositive relativeto thepres-I ure of'the roduet s ace portion alongside. As a onsequence, it is believed, without such belief beinga' limita'-. tion on this invention; that some combustible gases" pass through the intersticesfl-lla and through' the interstices tag but considerably.moreicleaning than tliv oil? through oifstake" 76 at the rear} or the furnaces'ection 25B. .Each cleaner 99 may beoue of 'ari electro static nature, such as the Cottrell type, and the efiiuent therefrom will be relatively clean; relatively and non-combustible g as'whichin eithercase may be supplied to one or moreflof thearch jets 56,"thepressurizing'-nozzles 54, the curtain nozzles 57," or the purge pipes and between thecap tiles 41jand burnas schematically illustrated in Figure 16' on the outer surfaces of the wall of mutfi'e' 39 in product s p'ace 31c and keep such surfaces relatively free of. carbonaceous adhesion; deposit and buildup which otherwise would forcefunwante'd shutdowns. "Sti ll' further, the pressure relation between chamber 39 and product space 31c is maintained close enough that the gases passing out through the interstices,

such as interstices 40h, dojnot impinge or reach, the laterallyi adjacent .electrodeslQand thusavoid burning or l'fig idepending'iiupon the quantityand the relative need in a particular section or at a particular location; in the equipment lil. Q.

, The burnersf67 maybe supplied'with combustion air by a blower 100, such combustion air passing into the gooseneck members, 68 through a pipe 101 and manifold 192.." A manifold 103"connected to blower may be used to 'supplycombustion air to 'the pilot burners 74, the arrangement on leach sideubeing duplicated on the opposite side. G as forthepilotburners is supplied 'to' i 1 a manifoldth'rough a pipelM' from .a' fuel gas source 105. That same source may be used to conduct fuel gas l through a pipe 106 to the "throat of a venturi'inspirator making the 'surfacesof those electrodes relatively porous:

or spongy. At the same time, soot from cracking of hy-' drocarbons and particulate matter which 'isl produced:

and in the atmosphere ofproduct space 31c plus hydrogen therein from i cracked hydrocarbons are urged .to flowjtowardproduct space portion 31b in preheating'sec tiori 35 A by the arch jet 56 at the rear end of section 3513;

l Such inhibits the'flow of soot in the atmosphere into the cooling section 43 where such jso'ot would otherwise I have a tendency to settle out on "the cooling pipes '43a been-made to the supplementary, or alternative, functionf form of theburnable contaminants and hydrogen in the tunnel atmosphere to prevent those contaminantsfrom building up on the muffle walls or other partsof the furnace equipment, or both; to the---'detriment of the operation. The mantenance of thatpressure relationship of the mufliewchambers 36 isinfluenced by a variety of fac- 107 operated bya primaryfairjblower"103, the fuel and primary partial combustion, air passing through a pipe 109 to a manifold 110 and fromthenceto the gooseneck portions of the burner 42,?the arrangement forwhicli is duplicated again on the opposite side ofpfurnace '10; Secondary combustion airfor the burners '42'issupp1iecl 1 through alpipe 1.11 from blower source 190 preferably lower'their cooling efliciency. Reference has already Y "ing of the offtake 76' atthe rear endof furnace see;

after indirectjheat ex'changeat with ahotterlfluid body such I asthe combusted "gases discharged from the drums 73m] The other heat exchangers shown onl'the diagramfof Figure '18 are als'ofrnanked '112 iriasmuch as they 'too may draw; upon such) effluenti gases, from the drum 73a as their thermal: head source b'efore such gases are discharged to-,the stack, orthethermal head source may be the efiiue'nt gases from the drums 89 whichotherwise might be sent to the stack dependent upon the needs of -the, system at the timejbeing; e;g., thesys'tem will tors includingthe -numbe'r of burners 67 placed in ope'ration, the number ofiburners 42 placed 'in operation, the adjusted size of the openings -92, ifl'eft open, the amount of gas generated byuthe preheating and baking -of the electrodes ,-the control regulation imposed upon the furfiace 10,- to-men'tion' some; although notal-l, of the; factors Q t which would beltakeninto accountinheating up theapparatus. for the" first time-preparatory to use. In' the eventthat iriterstices are left between 1116163168 37 and 38- a inl'the'inuffle walls-"of the -chambers, less dependence will have to be-placdupon provision for ducts'Y'llg-andv of a conventionalxtype. I placed'under suction by a fan 117' which-has a master motor operated valve 118, in the suction "line 7 therefor.

in some fcases 'suchdu'cts' maybe entirely, omitted if R 7 l re1-8Qa schematic:layoutlisshown of aflexible J V coutrol lsystem which may be' impressed 4 upon the-{illus 6 emb diment --of v this invention i for t the additionalf rgulation need i I t have moreneed of conserving heat'in afcolder' weather 40 season than it will in a warmer weather season. .By-passes 113 may be" provided a'round the'res'pective heat exchangers. V- t H k a a Forjautomatic regulation lof the pressure in the muffle chambers, a control system may be employed'and one form thereofvis illustrated inFigure"l8.- For flexibility,

such a control is applied to each of themuifle chamber systems'being those respectively'in the preheating section 35A and in thelfurnace 'section35B., Thus, in the system for section 35B, pipes 114 are provided with'rnotorcontrol Valves 115 respectively responsive to controllers 116 The pipes 114 join'fand are t a selected speed by'a motor 1 19.

a a Of-D 9 'lii ch' will be the" t the naa; 1 as" h t, u ra i- 9 Fi al "to be treated such as.corhonacequspele t d .Tas .anrillustration only, be gradually raised .in temperature 9 An independent but corresponding control to which the same reference numerals have been applied with the addition of a prime accent thereto is utilizable for control of the pressure relationship in the muffle chambers 36 as shown on Figure 18. Such independent control system for the preheating section mufiles 36 also means that the two mutfie chamber sets 36 and 39 may be operated independently as when the dampers 91 are fully closed on both sides of the furnace. In the case of the .effluent gas 6 through the preheating pipes 34, are drawn out by a fan 117' and sent to a chimney stack 124 for discharge. Whenever the product space atmosphere is drawn into the muflle chambers 36 in the preheating section 35A through the interstices of the mufile wall in significant quantity, a regular burner to which fuel is supplied in the regular manner may be utilized at the rear of each chamber instead of using aspirating burners 67 shown in the illustrated embodiment.

On the other hand, the muffle chamber efiluent gas from drums 89 may be regulated by virtue of the feed to the burners 42 such that the combusted eflluent is sufficiently non-oxidizing to warrant all or a portion thereof being taken out througha pipe 125 and a branch 126 for passage through a cooler 127 and a cleaner 128 which may be of a kind previously described in connection with the coolers and cleaners 98 and 99 respectively. If desired, a cooler or heat exchanger may also be inserted in the pipe between the drums 89 and the fan 117. Clean, cool non-combustion .gasdischar ged from cleaner 128 may also be utilized to go to one or more of the purge inlets 25 and 26, the curtain nozzles 57, the undercar pressurizing nozzles 54, or thearch jets 56, or allof them, depending upon the supply available. When the gas from the drums 89 is not so diverted in Whole or part, it may be discharged through a chimney stack 130., A pressure relief valve 129 may also be placed at the top of the crown of furnace for safety or partial regulation purposes and, further, maybe connected to an open air flare; burner, if desired. P 7 v p The finished product on the cars 17 leaving the furnacesection 35B pass into a cooling section 4i having a plurality of transversely arching pipes 43a as shown in detail in Figure 5. The lower ends of the respective pipes are'supported by andin communication with 'plenunis I 131 onthe benches 29 on each side of the product space 31d: The cooling section is providedasa plurality longitudinally. succeeding subsections each subsection. having a pair of plenums. 131 on oppositesides', v-A blow- 21200'F. opposite the foremost of the burners 42 and theremaintained at that temperature until the product enters cooling zone 43 wherein thefinished product is gradually reduced in temperature toabout 250 F. before the car 17 hearing it is separated in the purge vestibule:

12 from whence it is taken into the air. The product baking cycle in the illustrated embodiment has the char: acter of a continuous operation even though the conveyor, in the form of cars 17, are moved in this embodiment intermittently. and is very short. Thus, the cycle time for a particular electrode from start to finish maybe accomplished in a period varying according to the size and nature of the product and ranging from one day in some cases to a week in others. I

The finished electrode product-19, one form of which is illustrated in Figure 17 with a recess 19' in the dome thereof, produced by thisv invention has a unique uni: formity of composition and; reproduciblity as well ,as a silvery metallic gray finish which'requires no cleaning or. grinding to fitit for use. Further, in use, product such as electrodes produced by this invention fora metal salt reducing bath such as an aluminum-making operation are less subject to spalling or other deterioration. Various changes may be made in the details of the illustrated embodiment and practices and'otherembodimerits may be provided without departing from the spirit of thisinvention, or the scope of the appended claims. We claim: 4 p i -11, In a closed tunnel kiln appaTatus comprising, in combination,;'enclos ed entry and exit vestibule chambers, meansfor purging said first-named chambers, a longitudinal product chamber extending between said first:

named: chambers, means to inhibit access into said prod-.

uct chamber by outside air, a mufiie chamber on each sideof said product chamber, each of said muffle chambers having an inner wall made up of interfitting refractor y sections, longitudinally close fitting cap members i extending between said inner wall and the adjacent side of said kiln to closethe top of said mufiie chambers, a baflie, projecting transversely into each of said 'muflie chambers to define an adjustable optional passage between avforward portion thereof and a rearward portion thereof, burners at least in said rearward portion, means to provide apreselectedpressure in said rearward portion positive relative to the pressure in the laterally ad-- joining portion of said product chamber to forcecombusting'gases fromjsaid rearward portion ofsaidmufiie chamber. generally laterally to' the outer face ofthe innerwallithereof toburn adjacent said face, means to providea p'reselected pressure in'said forward portion somewhat negative relative to the pressure in the laterally adjoining portion of the product chamber to draw product er '132is'used to force airinto' amanifoldISS whichl'isl itions 3sli' may beutilized,gifbdesirei aswa source: of

heat dcombustionairl'forthegburners in one or t ereof the iriuflie 'chamber section's, as will be undefstood by thoseto thiskinve ntionis disclosed. In ,thecoolin se'crie the electrodes ,19, for like product-are brought s 9 a safe em ratu t'w 'h y l ,iwtb a when'they moveinto the open air after passing through vestibule 12. v, In practice anembodi 0 "his n i i y i a i t e Produ 1Q 0, F. to about 450 F. -in;preheating' section 33; furtherbe gradually raised in temperature 'in preheating section 35Ato about 1700" F andstill furtherbe graduallyraised intemperature'infilrnace section 35B to about,

'spaceatrnosphere generally laterally into said forward portion of said mufileflchambers, and means for with drawing gases from said muffle chambers. In a 'tulrinel kilnf apparatus comprising, in com; bination',"a longitudinal productfchamber, a mufiie cham ber separated therefrom by awall on'eac'h side of said productcharnber," a damper projecting transversely into each-of s'aid-rnufiie charnbers'w-to' define an-adjustableoptional'passage between a forward portion thereof and a rearward'portion thereof, means to inhibit'access into said vproduct chamber at least adjacent said muflle charn bers by .outside ainburners at least in said rearward portion, meansto provide a preselected pressure in said rearwardportion positive relative to;thepressur,e in the laterallygadjoining portion of said product-chamber to force.combusting gases from saidsrearward portion of said rnuflle chamber in a generally lateraldirection to the f f'said wall in said product chamber, means to pro ide. 'a preselected pressure in said forward portion somewhat 'negatiyerelative to'the pressure inthe laterally adjoining portion of the product chamber to draw product space atmosphere into said forwardportion ofsaid mufiie chamber, and means for, Withdrawing gases 'fr omsaid mufii hambersp I of saidfrespective'vestibules, means to inhibit access into said product-chamber by outside-air, a preheating pipe sectioni adjacent said entry vestibule, sa'id preheating pipe section having a. longitudinally extending trough along 7 side of said preheating pipe; section to conductbcombusted gases forwardlythrough said pipes, a'preheating mufiie section adjoining said preheating pipe section to the rear thereof, a preheating muflie chamber in said' preheating mufile sectionon each sideof said product chamber, each of vsaid muifie chambers having .an upstanding refractory wall to preheat indirectly product in said product chambena burner in each of said mufile chambers, means to .draw product chamber atmosphere into each of said'preheating muffle chambers, ofr'take means connecting said mufile chambers to said preheating pipes, a heating section adjoining said preheating muffie section to the rear thereof, a,mufi ie chamber in said heating section on each side of said'product chamber, said secorid-named m'ufile chambers being in. communication with saidfirst-named mufllechambers through an adjustable optional passage, each of'said second-named muflle chambers having an upstandingrefractory wall to heatj indirectly product in ,said productchamber, means including a damper movable transversely to regulate the size, ofsaid-passagetto selectively maintain said secondnanred mufiie chambers somewhat positive in pressure relative to; the pressure 5 in, said product chamber and; to

maintain said first-named m ufi le chambers somewhat negative relative to the pressure in said product chamber, means. to permit combustible gasesfrom said second-named muffle chambers to pass through the walls thereof into said product chamber to burn close to said walls, andacooling section extending rearwardly of said heating section substantially to said exit vestibule.

p 10. Ina closed tunnel kiln for carbonaceous electrodes or the like as set forth in claim 9, said cooling section having cooling pipes arching across the top of theproductfi'ghti mber in said cooling section and extending downwardlyalong the respectivesidesthereof, plenums connecting the. lowerends of groups of adjacent cooling pipes, means for circulating cooling fluid through said gases from said kiln, means for cooling and cleaning said last-mentioned gases, and means for returning such cleaned gases to said kiln.

11. Apparatus for heat treating carbonaceous products or the'like, comprising, in combination, a'longitudinally extending refractory tunnel defining a space through which product is moved, an indirect lower temperature pipes, means for withdrawing non-combustion supporting preheating section in the forepart of said tunnel, a higher p temperature mufile section behind said preheating section, a still higher temperature mufilesection behind said higher temperature muffle section, a cooling section behind said'still higher temperature muffle section, means for independently regulating the mufiie pressure in said mufile sections relative to the pressure in said product space, means for regulating communication; between the mufiles in said respectivernuffle sections and said product space to at least withdraw product space atmosphere from said product space through the interior of a rnufile section by said communication, means for conducting a predetermined volume of gases discharged from said higher temperaturemufiie section into said preheating section, ofitake means for remaining such gases, means for passing a fluid coolant through said cooling section,

means for substantially excluding combustion-supporting gases from said product space, andmeans for withdraw- I being positioned rearwardly of said muffle heating zone, I

tunnel by outside, air, atmosphere locks at the ends of said tunnel, means-for admitting non-combustion supporting purge gases .into said atmosphere locks, an indirect lower temperature preheating section in the forepart of said tunnel, means for condensing collecting and withdrawingmaterial in said lower temperature preheating section,a higher temperature preheating mufile section behind said first-named preheating section, means for withdrawing atmosphere from said product space into the interior of said higher temperature muffie section to be burned therein, a still higher temperature muflle section behind said higher temperature preheating mufile section, means for bleeding a portion of the combustible gases in said still'higher temperature muffle section into said product space -,adjacent said last-named mufiie sectionrespectively, a cooling section behind said still higher temperature mufile section, means for passing a fluid coolant through said cooling section, means for substantiallygexcluding combustion-supporting gases from said product space, and means for withdrawing atmosphere fromsaid product space for cleaning and recirculation thereto.

13. Apparatusas set forth in claim 12, having means for longitudinally discharging non-combustion supportinggases adjacentthe underside of the top of said tunnel to inhibit longitudinal circulation of atmosphere in said such as electrodes or the like, steps comprising, in combination, conveyingmolded self-supporting unbaked product on a conveyor with said products moving through a product zone and said conveyor moving through a conveyorzone, supplying a non-combustion supporting atmosphereto said product zone at a pressure somewhat above atmospheric, at least part of said first-named-supplyinggbeing directed toward the discharge end of said product zone, substantially sealing ofi said product zone from said conveyor zone, supplying a non-combustion supporting atmosphere to said conveyor zone at a pressure slightly below the pressurein said product zone, said second-named supplying being directed toward the entrancelendof said conveyor zone, providing a preliminary preheating zone along the path of said conveying of said product in said product zone, condensing condensibles from the atmosphere in that'portion of said product zone alongside said preliminary preheating zone,

collecting condensibles so condensed and other liquids present in said-preliminary preheating zone in thelbot tom of said conveyor zone for withdrawal of such liquids therefrom, providing a muille preheating zoneralongside the path of said conveying of said product in said product zone, said muffie preheating zone being positioned rearmuffle heating zone alongside the path of said conveying of said product in said product zone,tsaid muffle heating zone being positioned rearwardly of said muffle preheating zone, regulating the pressure in said muffle heating zone to bleed combusting gases through the boundary of said mufiie heating zone into said product zone closely adjacent only to said boundary of said muflle heating zone, withdrawing non-combustion supporting gases from at least oneof said zones, cleaning said non-combustion supporting gases so withdrawn, recirculating at least part of said non-combustion supporting gases so withdrawn and cleaned to at least one of said zones, providing an indirect cooling zone around the path of said conveying of said product in said product zone, said cooling zone and supplying a cooling fluid to the interior of said 0001- ing'zone to reduce'the temperature o fsaid'pr'oduct below the flammable temperature thereof in air.

'15. Ina method forpreparing carbonaceous products or the like, steps comprising,incombination, conveying -molded laterally self-supporting unbaked production a conveyor with said productsmoving through a productt zone and said conveyor moving through a conveyor zone, supplying a non-combustion supporting atmosphere to said product zone at a pressure somewhat above atmosphen'c, supplyinganon-combustion supporting atmosphere to said conveyor zone at a pressure slightly above atmospheric, providing a muffle preheating zonealongside the pathof said conveying of said product in said product zone, regulating the pressure inside said muffle vpreheatingzone to withdraw atmosphere from said prod- 1 net zone toburn in said 'mufile preheating zone, providing a'muffle heating'zone alongside the path of said conveying of said product in said product zone, said muffle heating zone being positioned rearwardly of'said muffie preheating zone, regulating the pressure in said muflle heating zone to bleed-combusting gases generally: laterally into said productzone to burn closely. adjacent reginaaagme pressure inside said rnufiie preheating zone to withdrawatmospherefrom'said productspace to burn proximately in said muflilepreheating zone,= providing a' 'rnuffl'e heating zone alongside the path of said conveyingof'said product in said product space, saidmufile heating zone being positioned rearwardly of said 'rnufile preheating 'zone, and regulating the pressure in said'mufiie heating zone to forcecor'nbusting gases infrestricted quantity into said productspace toburn closely adjacent tosaid mufiie heating zone. I If I 17; In a muffle combustion method for preparing carbonaceousproducts or the like, steps comprising, in combination, moving product through an enclosed product s'pacefsupplying a non combustion supportingatmosphere to'said-product spacefproviding a muftleheating zone alongside the pathof; saidconveying of saidproduct in only to said muffle heating zone,"discharging non-corn V bustion supporting gases into respective portions of said product zonealongside saidfmuffie zones in selected directions and adjacent the top of said portionstoinhibit longitudinal circulationbetween said muflle zones, with .dravvingnon-cornbustion supporting gasesfrorn at least onefof saidzones, cleanin'gsaid non-combustions'upport-g inggases'so withdrawn, recirculating at least part of said producfspa'ce, supplying a'non combustionsupportingnon-combustionsupporting gases 'so withdrawn 1 and cleaned to at least one of said zones, and cooling said product in said productz one-rearwardly of said muflie heating' zone to reduce the temperature'of saidp'roduct low the flammabletemperature thereofin air; 16. In a mufl lecombnstion method for preparing carbonaceous products or the like, steps comprising, in com bination, conveying product through an enclosed product space, supplying a non-combustion supporting atmosphere tosaid product space at a pressure above atmospheric, providing a muffle preheating zone alongside the path of said conveying of said product in said product space,

said product 'space,--andregulating the pressure in said muifle heating-zoneto' force combustion gases in re strictedquantity into said product space to burn closely adjacent to said mufiie heating zone.- I

518;" In amuffle combustion rnethodfor preparing carbonaceous products or the like steps comprising, in cornbination,- conveying r product through an enclosed 'atniOSPhere'to said product space at 'fapressure above atmospheric, providing a inu'flle'zon'e alongside the path of said conveying of said product in said product space,

regulating thepressure inside said muflle zone to withdraw atmosphere fromsaidproductspace toburnproximatelyin 'sa id muflie z'oneJf v V v d I References Cited in thefile of this patent V s i :UNITED STATES PATENTS 1,556,208-

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 2,983,022

May 9, 1961 Philip d'H. Dressler et a1.

It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent. should read as "corrected below.

Column 1, line 17, for "or" read for column 8, line 3, for '25B" read 35B line 55, for "conrtol" read control column 9, lines 59 and 60, for "sections" read section line 70, for "corbonaceous." read carbonaceous column 11, line 57, column 12, line 17, and column 16, line 18, for "combustion", each occurrence, "read combusting Signed and sealed this 17th day of October 1961,

(SEAL).

Attest:

ERNEST W. SWIDER Attesting Officer DAVIDL. LADD Commissioner of Patents USCOMM-DC- 

